In order to exploit solar energy, use is made of solar-thermal power plants in which the insolation is captured in the form of a plurality of silvered parabolic troughs connected in series and/or parallel, and is reflected onto an absorber line. Transported in the absorber line is a heat carrying medium that absorbs the thermal energy obtained from the irradiation and transports it further for the purpose of generating steam in the solar power plant. The silvered parabolic troughs have a support structure on which the silvered elements are arranged and made to track the sun's path. The mirror elements, and thus also the parabolic troughs have an aperture (distance between the outer mirror edges) of approximately 6 m. A parabolic trough collector may comprise a plurality of elements which are respectively arranged rigidly on the distortion-resistant parabolic mirror support structure. In this case, an element is then located between two spaced-apart support pylons or support posts that support it. The individual elements are of identical design, and between two elements connected one behind another in series there is located in the middle between two support pylons or support posts a drive unit with the aid of which the two elements or all the elements forming a parabolic trough collector can be made to track the sun simultaneously and uniformly on one axis. The movement is usually effected here with the aid of hydraulic cylinders that use levers, which are connected to the parabolic mirror support structure, to rotate the parabolic mirror support structure in the form of a lattice frame about a rotation axis. Here, the construction in the case of plants known in practice is such that the rotation axis runs above the mirror surface, or at least at the point of origin or vertex of the parabolic mirror curve. The result of this is that the mirror surface is interrupted in the longitudinal direction of the parabolic trough collector in the region where the drive unit effecting the swiveling of the elements of the parabolic trough collector, and so it is not possible to design the entire length of a parabolic trough collector as mirror surface for utilizing sunlight. Moreover, it is necessary in the case of this construction to provide solid gusset plates at the final points of turning and rotation of a collector element in order to be able to absorb and transmit the forces of rotation and torsion occurring here.
As is known, for example, from the generic WO 2005/066553 A1, there are, however, also constructions in the case of which instead of a torque lattice frame the parabolic mirror support structure has a torsion tube that supports the parabolic mirror support structure. However, even in this case the drive unit is arranged between two parabolic trough collector elements and effects an interruption of the parabolic mirror surface of the parabolic trough collector. The parabolic trough collector longitudinal rotation axis, cooperating with the actuating element to move the parabolic mirror support structure, of a primary plate there is arranged in the radial direction of the primary plate of the central longitudinal axis of the torsion tube supporting the parabolic mirror support structure.
Also known in practice are torsion tubes that have lugs which are welded on the outer periphery and on which support frame structures are fitted, on which the mirror surfaces are fastened. With such torsion tubes it is then necessary to fit on the outer lateral surface support elements that form the absorber support structure and support the absorber tube, and this is done by welding, in particular. Such support elements are approximately two meters long and in the event of a rotational or swiveling movement of the parabolic trough collector into a tilted position transmit a substantial torque, and thus a substantial force onto the welded seam on the lateral outer surface of the torsion tube by means of which these are fastened on the torsion tube. These torsion tubes are also usually mounted between two support pylons or support posts, such that these exhibit a greater flexure than a lattice frame support structure that extends over a plurality of support pylons or support posts.
The essential disadvantage of the design of known parabolic mirror support structures for forming a parabolic trough collector therefore consists in the fact that it is impossible to form a mirror surface that is continuous in the parabolic trough collector in the longitudinal direction, because there are formed between individual elements or parabolic trough collector sections there support pylons or drive pylons that project into the region of the mirror surface such that transverse strip regions in which no mirror elements or no silvered surface can be arranged are always present. Moreover, the known lattice frame constructions incur relatively high production costs occur because of the expensive metal construction and the need to provide gusset plates for transmitting the forces for the purpose of tracking the parabolic trough collectors.